Lidar sensor for vehicle apparatus

ABSTRACT

Techniques for realizing compound semiconductor (CS) optoelectronic devices on silicon (Si) substrates for vehicle applications are disclosed. The integration platform is based on heteroepitaxy of CS materials and device structures on Si by direct heteroepitaxy on planar Si substrates or by selective area heteroepitaxy on dielectric patterned Si substrates. Following deposition of the CS device structures, device fabrication steps can be carried out using Si complimentary metal-oxide semiconductor (CMOS) fabrication techniques to enable large-volume manufacturing. The integration platform can enable manufacturing of optoelectronic devices including photodetector arrays for image sensors and vertical cavity surface emitting laser arrays. Such devices can be used in various applications including light detection and ranging (LIDAR) systems for vehicle apparatuses such as automobiles, boats, airplanes, and drones, and for other perception applications such as industrial vision, artificial intelligence (AI), augmented reality (AR) and virtual reality (VR).

BACKGROUND OF THE INVENTION

Electronic devices have proliferated over the years. From an iPhone 12designed and sold by Apple Inc. to advanced networks for selling almostany type of good by Amazon.com Inc., electronic devices have enteredinto almost every aspect of our daily lives. These devices rely onminiature chips made from semiconductor materials, commonly silicon(“Si”). These silicon materials are also used to make sensing devicesthat can capture images of objects or scenes. Silicon is widely usedbecause it is an abundant material and silicon-based semiconductormanufacturing is mature due to the investments made in the electronicsindustry. A common technology process is called complementary metaloxide semiconductor, or “CMOS.” The CMOS technology was developed formanufacturing integrated circuits but is now used for image sensors.Such image sensors are called CMOS image sensors. Often times, such CMOSimage sensors are manufactured using high-volume manufacturing with12-inch silicon wafers.

Despite the advances with CMOS image sensors, limitations or drawbacksexist. For example, CMOS image sensors have limitations in thedetectable wavelength range. Additionally, such CMOS image sensorssuffer from poor sensitivity at longer wavelengths within the detectablewavelength range. These and other limitations may also exist.

From the above, it is desired that industry develop improved sensingdevices.

BRIEF SUMMARY OF THE INVENTION

The present invention is generally related to electronic devices. Morespecifically, the present invention provides techniques related tooptoelectronic devices for vehicle applications such as, but not limitedto, photodetectors and photodetector array circuits using heteroepitaxyof compound semiconductor (“CS”) materials on silicon, along withsubsequent circuit fabrication and integration methods. Merely by way ofexample, the present invention can be applied to various applicationsincluding image sensing, range finding, including LIDAR (light detectionand ranging), among others, but it will be recognized that there aremany other applications.

According to an embodiment, the present invention provides a vehicleapparatus configured with LIDAR functionality. The vehicle apparatusincludes a vehicle with a drive mechanism configured to spatially movethe vehicle (e.g., from a first location to a second location). Thevehicle can include any type of automobile, watercraft, aircraft, hybridvehicle, unmanned vehicle, or the like. The drive mechanism can includevarious types of power sources (e.g., engines, motors, batteries, etc.)configured to moving mechanisms (e.g., wheels, propellers, legs, etc.).

One or more module devices can be configured to an exterior region ofthe vehicle (e.g., a roof portion, a front portion, a side portion, aback portion, etc.). The module device can have a housing with anexterior region and an interior region. The exterior region includes asensing portion and a detecting portion.

The sensing portion of the module device can be coupled to a laserdevice (or laser array) configured to emit electromagnetic radiation.This laser can be spatially disposed to include an aperture configuredon the sensing portion of the exterior region of the housing. Theelectromagnetic radiation emission can have a wavelength range between850 nm to 1550 nm. The laser device can be a VCSEL (vertical cavitysurface emitting laser) array device, an EEL (edge emitting laser)device, a laser device coupled to a mirror device, or the like.

The detecting portion of the module device can be coupled to an imagesensor device configured to detect photons and convert them toelectrical signals. This image sensor can be spatially disposed toinclude an aperture configured on the detecting portion of the exteriorregion of the housing. The image sensor can be coupled to alogic/readout circuit and the laser can be coupled to the laser driver.These devices can be configured within the same integrated circuitdevice.

The module device can further include a classifier module coupled withinthe interior region of the housing. In an example, the classifier modulecan be coupled to the logic/readout circuit to further process the datacollected by the image sensor. This classifier module can include aclassification of one or more classes including a speed sensing, imagesensing, facial recognition, distance sensing, acoustics sensing,thermal sensing, color sensing, biosensing (i.e., via a biologicalsensor), gravitational sensing, mechanical motion sensing, or othersimilar sensing types.

In a specific embodiment, the image sensor includes a photodetectordevice, which includes, among other elements, a first terminal and asecond terminal. The photodetector device includes a Si substratecomprising a surface region. The device has a buffer material comprisinga CS material deposited on the surface region of the Si substrate usingdirect heteroepitaxy such that the CS material is characterized by afirst bandgap characteristic, a first thermal characteristic, a firstpolarity, and a first crystalline characteristic, and the Si substrateis characterized by a second bandgap characteristic, a second thermalcharacteristic, a second polarity, and a second crystallinecharacteristic. The device has an array of photodetectors, the arraybeing characterized by N and M pixel elements, where N is an integergreater than 7, and M is an integer greater than 0.

In an embodiment, each of the pixel elements has various features. In anembodiment, each pixel element has a characteristic length ranging from0.3 micrometers to 50 micrometers. In an embodiment, each pixel elementhas a preferred characteristic length ranging from 0.3 micrometers to 50micrometers. In an embodiment, each of the photodetectors comprises ann-type material comprising an indium phosphide (InP) material comprisingan Si impurity having a concentration ranging from 3E17 cm⁻³ to 8E18cm⁻³, an absorption material overlying the n-type material, theabsorption material comprising indium gallium arsenide (InGaAs)containing material, the absorption material being primarily free froman impurity, a p-type material overlying the absorption material, thep-type material comprising a zinc impurity or a beryllium impurityhaving a concentration ranging from 3E17 cm⁻³ to 5E18 cm⁻³, a firstelectrode coupled to the n-type material and coupled to the firstterminal, and a second electrode coupled to the p-type material andcoupled to the second terminal to define a two terminal device. Thedevice has an illumination region characterized by an aperture region toallow a plurality of photons to interact with the CS material and beabsorbed by a portion of the absorption material to cause a generationof mobile charge carriers that produce an electric current between thefirst terminal and the second terminal.

Optionally, the device has a responsivity (Amperes/Watt) greater than0.1 Amperes/Watt characterizing the circuit, and a photodiode quantumefficiency greater than 10% characterizing the circuit.

Benefits or advantages are achieved over conventional techniques. Theintegration platform based on heteroepitaxy of CS materials and devicestructures on Si by direct or selective heteroepitaxy enableslarge-volume manufacturing of optoelectronic devices, such as imagesensor and laser arrays, for use in vehicle applications. These devicesfabricated using the present techniques can exhibit improved detectablewavelength range, higher sensitivity, and other related performancemetrics. These and other benefits or advantages are described throughoutthe present specification and more particularly below.

A further understanding of the nature and advantages of the inventionmay be realized by reference to the latter portions of the specificationand attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1A is a simplified diagram of a top-view of a LIDAR device for avehicle apparatus according to an example of the present invention;

FIG. 1B is a simplified diagram of a perspective view of an exampleimage sensor array chip of the LIDAR device shown in FIG. 1A;

FIG. 1C is a simplified diagram of a perspective view of an examplelaser chip of the LIDAR device shown in FIG. 1A;

FIG. 1D is a simplified diagram of a perspective view of an examplelaser chip of the LIDAR device shown in FIG. 1A;

FIG. 1E is a simplified diagram of a front perspective view of a vehicleapparatus with integrated image-sensing according to an example of thepresent invention;

FIG. 1F is a simplified diagram of a back perspective view of a vehicleapparatus with integrated image-sensing according to an example of thepresent invention;

FIG. 1G is a simplified block diagram of a LIDAR system according to anexample of the present invention;

FIG. 2A is a simplified diagram of a circuit device including aphotodetector array circuit coupled to a readout circuit according to anexample of the present invention;

FIG. 2B is a simplified circuit diagram of the photodetector arraycircuit coupled to the readout circuit shown in FIG. 2A;

FIG. 3 is a simplified diagram of a photodetector circuit deviceaccording to an example of the present invention;

FIG. 4 is a simplified diagram of a device including CS buffer materialson a Si substrate realized by heteroepitaxy according to an example ofthe present invention;

FIG. 5 is a simplified diagram of a device including CS buffer materialsand CS device materials for a photodetector on a Si substrate realizedby heteroepitaxy according to an example of the present invention;

FIG. 6 is a simplified diagram of a device including CS buffermaterials, CS device materials, and p-doped regions formed by diffusion,on a Si substrate realized by heteroepitaxy according to an example ofthe present invention;

FIG. 7 is a simplified diagram of a device including CS buffermaterials, CS device materials, p-doped regions formed by diffusion,isolation trenches, a planar film, metal contacts, vias, metal in vias,and top metal formed in trenches, on a Si substrate realized byheteroepitaxy according to an example of the present invention;

FIG. 8 is a simplified diagram of CS buffer materials and CS devicematerials deposited on a Si substrate realized by selective areaheteroepitaxy that leverages a patterned dielectric according to anexample of the present invention;

FIG. 9 is a simplified diagram of CS buffer materials, CS devicematerials, p-doped regions formed by diffusion, isolation trenchesformed, a planar film formed, metal contacts formed, vias formed, metalin vias formed, and top metal formed in trenches, on a Si substraterealized by selective area heteroepitaxy, according to an example of thepresent invention;

FIGS. 10A-10C are a top view description of a wafer with patterned dieand top view descriptions of example dies patterned with circles orrectangular stripes for selective area heteroepitaxy, respectively,according to an example of the present invention;

FIG. 11 is a simplified flow diagram illustrating a method tomanufacture photodetectors and photodetector array circuits leveragingdirect heteroepitaxy or selective area heteroepitaxy on a Si substrate,and the subsequent wafer-to-wafer bonding integration with a readoutcircuit wafer, followed by backside processing, according to an exampleof the present invention;

FIG. 12 is a simplified diagram illustrating a plot of the approximateabsorption spectra for InGaAs material, which is used in the presentinvention, and Si material, which is used in conventional CMOS sensingdevices.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally related to electronic devices. Morespecifically, the present invention provides techniques related tooptoelectronic devices for vehicle applications such as, but not limitedto, photodetectors and photodetector array circuits using heteroepitaxyof CS materials on Si, along with subsequent circuit fabrication andintegration methods. Merely by way of example, the present invention canbe applied to various applications including image sensing, rangefinding, including LIDAR, among others, but it will be recognized thatthere are many other applications.

In an example, the present invention provides method and device forrealizing highly manufacturable and scalable semiconductoroptoelectronic devices, including photodetector circuit arrays, on Sisubstrates that can be implemented in a variety of vehicle apparatuses.By directly depositing CS materials on Si substrates, mature Simicroelectronics manufacturing processes can be leveraged to fabricatehigh performance photodetector circuits. Deposition on 12-inch Sisubstrates, which are common for CMOS technologies, enables thesubsequent fabrication in CMOS manufacturing lines, however, thetechnology is not limited to 12-inch Si substrates only. CS materialscan be deposited directly onto Si substrates with the techniquesdescribed in the present invention.

The technique to describe the direct deposition of CS materials isreferred to herein as heteroepitaxy. The heteroepitaxy step or steps maybe carried out with techniques including, but not limited to,metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy(MBE), metalorganic MBE (MOMBE), chemical beam epitaxy (CBE), hydridevapor phase epitaxy (HVPE), liquid phase epitaxy (LPE), or anycombination thereof.

In addition to Si substrates, alternative substrates may be usedincluding, but not limited to, silicon on insulator (SOI), miscut Si,SOI on miscut Si, or germanium (Ge) on Si, without departing from thescope of the invention.

In an embodiment of the present invention, CS material is deposited ontoa Si substrate by heteroepitaxy, by firstly depositing a buffer materialthat includes an initial nucleation on the Si surface and enables thetrapping, annihilation, and/or filtering of defects near the interfacebetween the CS material and the Si surface. The initial nucleation stepmay be carried out at a relatively low temperature, and the subsequentbuffer material growth intended to trap, annihilate and/or filterdefects may be carried out at a higher temperature. Surface treatmentmay be carried out prior to the initial nucleation on the Si surface.This treatment may include, but is not limited to, chemical cleaningand/or treatment of the Si surface, reordering of the Si surface withhigh-temperature annealing in an ambient, high-temperature annealing inan ambient to remove and/or treat a surface oxide, or the formation ofvarious Si crystal planes by treatment or etching.

The initial nucleation and buffer growth can be carried out with anumber of methodologies, and combinations of methodologies, including,but not limited to, initial group IV (e.g., Si or Ge material) growthfor surface reordering or reparation followed by CS growth for defecttrapping, or Si surface patterning or structuring, that may includeformation of various Si crystal planes, followed by CS nucleation andgrowth, or low-temperature CS nucleation, or low-temperature CSnucleation followed by multi-step growth with temperature grading fordefect bending and annihilation, or use of strained layer superlattices,interfaces with high strain fields, graded or step-graded layers, orother similar techniques to redirect, trap, convert, and/or annihilatedefects.

The techniques of the present invention can be used to manufacturevarious optoelectronic devices in high volumes by leveraging Simanufacturing methods. These devices include, but are not limited to,lasers that are either edge-emitting or vertical cavity surfaceemitting, optical modulators, photodetectors or photodiodes,semiconductor optical amplifiers, and nonlinear devices for optical combor frequency generation. Specific to image sensors and photodetectorcircuit arrays, various device structures could be realized byheteroepitaxy deposition of device layers and subsequent fabricationsteps. These device structures include, but are not limited to, planarphotodiodes, mesa photodiodes, double mesa photodiodes, PIN or NIPphotodiodes, avalanche photodiodes (APDs), and uni-traveling-carrier(UTC) photodiodes.

The optoelectronic devices and device arrays realized with deposition ofCS materials on Si can be leveraged in various applications, including,but not limited to, LIDAR; LIDAR for autonomous vehicles including, butnot limited to, automobiles, aerial vehicles, airplanes, jets, drones,robotic vehicles; advanced driver assistance systems (ADAS); LIDAR formobile devices including, but not limited to, phones and tablets;imaging for camera applications including, but not limited to, digitalcameras, mobile phones, tablets; imaging and perception for robots,artificial intelligence (AI) applications, augmented reality (AR)applications, and virtual reality (VR) applications; 3D imaging andsensing; defense and aerospace; industrial vision, factory automation;medical and biomedical imaging; topography, weather, and wind mapping;gas sensing; infrared (IR) imaging; smart building, security, peoplecounting; thermal imaging, thermography; heating, ventilation and airconditioning (HVAC);

In addition to the group III-V CS materials, the techniques of thepresent invention could apply to other materials for photodetectorcircuits including, but not limited to, II-VI compounds, IV-VIcompounds, II-V compounds, or IV-IV compounds.

In another embodiment, the CS nucleation, buffer materials andsubsequent photodetector materials may be deposited and formed byselective area heteroepitaxy, whereby the Si or similar substrate couldbe first patterned with a dielectric to form recesses, within which theCS nucleation, the buffer materials and the photodetector materialscould be selectively deposited. Selective area heteroepitaxy is theprocess by which the Si substrate would be patterned with a dielectric,and the subsequent deposition of semiconductor materials would depositselectively on the exposed Si surfaces but not on the dielectricsurfaces. Selective area heteroepitaxy is beneficial for improving thequality of the CS material on Si, for facilitating photodetectorfabrication, and also for realization of novel device structures.Selective area heteroepitaxy can improve material quality by releasingthermal strain caused by the mismatch in thermal expansion coefficientbetween the CS materials and the Si, and by providing aspect ratiotrapping of defects and dislocations.

The techniques described above can be applied to an integrated circuitconfigured for a vehicle apparatus. FIG. 1A is a simplified diagram of atop-view of a LIDAR device for a vehicle apparatus according to anexample of the present invention. As shown, device 101 includes acircuit board 110 (e.g., printed circuit board (PCB), or the like) witha readout/logic device 120, an image sensor device 130, a laser device(or laser array) 140, and a laser driver 150 configured on top. In thiscase, the image sensor chip 130 is bonded face-down overlying thereadout/logic chip 120. The laser array chip 140, configured by itsassociated laser driver 150, emits one or more output beams that arereflected off of a target and return to be imaged by the image sensorchip 130. FIGS. 1B-1D show additional details or variations for certaincomponents of device 101. FIG. 1B shows a perspective view of an exampleimage sensor chip 130 configured as an array 132 with M×N pixelelements. The laser array chip 140 can be a VCSEL (vertical cavitysurface emitting laser) array 142, as shown in FIG. 1C, an EEL (edgeemitting laser) 144, as shown in FIG. 1D, or the like. Example outputbeams 149 are shown by dotted lines in both examples.

According to an example, the present invention provides a vehicleapparatus 104 configured with LIDAR functionality. As shown in FIG. 1E(front perspective view) and FIG. 1F (back perspective view), an examplevehicle apparatus 104 includes a vehicle with a drive mechanismconfigured to spatially move the vehicle (e.g., from a first location toa second location). In this case, the vehicle is a quadcopter-type drone190, and the drive mechanism includes rotors 192, each of which can bepowered by a motor. The vehicle can include any type of automobile,watercraft, aircraft, hybrid vehicle, unmanned vehicle, or the like. Ina specific example, the vehicle can be selected from a boat, a drone, anairplane, a truck, an automobile, an autonomous vehicle, or the like.The drive mechanism can include various types of power sources (e.g.,engines, motors, batteries, etc.) configured to moving mechanisms (e.g.,wheels, propellers, legs, etc.). Those of ordinary skill in the art willrecognize the variations, modifications, and alternatives to suchvehicle types and their associated drive mechanisms.

One or more module devices can be configured to an exterior region ofthe vehicle 190 (e.g., a roof portion, a front portion, a side portion,a back portion, an underside portion, etc.). Here, the module device 105is configured on top of the vehicle 190 and includes a housing 160 withan exterior region 162 and an interior region 164. The exterior regionincludes a sensing portion 174 and a detecting portion 176. In thiscase, the sensing portion 174 and the detecting portion 176 areconfigured of the front-side of the exterior region 162. There can beother configurations, such as having the sensing and detecting portions172, 174 on the back side and/or both left and right sides of the modulehousing 160 or having additional module devices on different portions ofthe vehicle exterior region.

The sensing portion 174 of the module device 105 can be coupled to alaser device 140 configured to emit electromagnetic radiation. Thislaser 140 can be spatially disposed to include an aperture configured onthe sensing portion 174 of the exterior region of the housing 160. In anexample, the electromagnetic radiation emission can have a wavelengthrange between 850 nm to 1550 nm. In a specific example, the wavelengthrange is 940 nm. The laser device 140 can be a VCSEL array device (seeFIG. 1C), an EEL device (see FIG. 1D), a laser device coupled to amirror device, or the like.

The detecting portion 176 of the module device 105 can be coupled to animage sensor device 130 configured to detect photons and convert them toelectrical signals. This image sensor can be spatially disposed toinclude an aperture configured on the detecting portion 176 of theexterior region 162 of the housing 160. The image sensor 130 and laser140 can be configured similar to the integrated circuit device 101 shownin FIG. 1A. As shown in the interior region 164 (dotted line cutaway 106in FIG. 1E), the image sensor 130 is electrically coupled to alogic/readout circuit 120. In this case, the image sensor 130 is facingthe back-side of the device 105 (indicated by dotted lines). Further,the laser 140 is electrically coupled to the laser driver 150.

The module device 105 can further include a classifier module 178coupled within the interior region 164 of the housing 160. In anexample, the classifier module 178 can be coupled to the logic/readoutcircuit 120 to further process the data collected by the image sensor130. This classifier module 178 can include a classification of one ormore classes including a speed sensing, image sensing, facialrecognition, distance sensing, acoustics sensing, thermal sensing, colorsensing, biosensing (i.e., via a biological sensor), gravitationalsensing, mechanical motion sensing, or other similar sensing types.

In an example, the image sensor 130 is a photodetector circuit thatincludes a CS material stack formed overlying a Si substrate. Thismaterial stack can include a buffer material and an array ofphotodetectors configured from an n-type material, an absorptionmaterial, and a p-type material. Each photo detector also includes anillumination region, a first electrode coupled to the n-type materialand a first terminal, and a second electrode coupled to the p-typematerial and a second terminal. Further details of the photodetectorcircuit are discussed in reference to the remaining figures.

This module device 105 can also be configured for virtual reality (VR),a mobile phone, a smartphone, a tablet computer, a laptop computer, asmart watch, an e-reader, a handheld gaming console, or other mobilecomputing device. Those of ordinary skill in the art will recognizeother variations, modifications, and alternatives to the deviceconfigurations and applications discussed previously.

FIG. 1G is a simplified block diagram illustrating a LIDAR systemaccording to an example of the present invention. As shown, system 107includes an image sensor device 130, optics 134, a laser device (orlaser array) 140, a movable mirror 180 optically coupled to an opticalcirculator 136. In this configuration, the movable mirror 180 can steerone or more outgoing beams coming from the laser 140 (through theoptical circulator 136) to an object/point of reflection 199. Then, oneor more return beams from that object/point of reflection 199 are imagedwith the image sensor 130 (i.e., reflected back from the movable mirror180 and directed by the optical circulator 136 through the optics 134 tothe image sensor 130). Using this optical path between these elements(shown by the lines with directional arrows), the movable mirror 180 maysteer in 2D to enable 3D imaging of a scene or object. Of course, therecan be other variations, modifications, and alternatives to this exampleLIDAR system.

FIG. 2A is a simplified diagram of a circuit device 200 including aphotodetector array circuit 201 coupled to a readout circuit 202according to an example of the present invention. As shown, thephotodetector circuit 201 is bonded to the CMOS readout circuit 202 atthe bond interface 203. The steps for front-end fabrication of thephotodetector circuit and the CMOS circuit may vary in detail or order,without departing from the scope of the invention. In an example, eachphotodetector device structure in the array 201 is formed with an n-typeCS material 214, a CS absorption material 216, a p-type CS material 220(configured within a CS material 218), a p-metal contact 224 coupled toa first terminal 228 (i.e., the anode), and an n-metal contact coupledto a second terminal 230 (i.e., the cathode). The n-metal contact/secondterminal coupling may be made from the topside of the photodetectorcircuit, or from the backside, without departing from the scope of theinvention. These photodetector devices can be separated by isolationtrenches 222.

The readout circuit 202 comprises a Si substrate 240, which can includethe readout integrated circuits (ROIC) 242 and other front-endintegrated circuits (ICs). The metal layers of the readout circuit 202within the dielectric layer 244 can include terminals (e.g., first inputterminals 246 and second input terminals) that connect to the anodeterminals 228 and cathode terminals 230 of the photodetector 201 at thebond interface 203. FIG. 2B shows a simplified circuit diagramrepresentation of device 200 with the photodetector 201 coupled to thereadout circuit 202 with terminals for pixel read out 262 and triggering264. Those of ordinary skill in the art will recognize other variations,modifications, and alternatives to the configuration for metal contactsand terminal connections.

The steps for the backend fabrication, including bonding, backsidecontact, optical coating, color filter integration, or lens attachment,may vary in detail or order, without departing from the scope of theinvention. In an example of the invention, the Si handle substrate andsome of the CS materials (see substrate 210 and CS buffer material 212in FIG. 3 ) are removed from the backside of the photodetector circuitfollowing face-to-face bonding to the Si CMOS circuit. This removalprocess can be used to form an illumination region configured to allowlight to interact with the photodetector materials (e.g., CS absorptionmaterial). An optical coating 250 and/or color filters 252 may beapplied to the n-type CMOS material to assist in defining theillumination apertures for pixel elements. A lens array 254 may becoupled to the optical coating 250/color filter 252 for increasing thecoupling of light to each pixel element to improve the responsivity ofthe photodetector circuit. The photodetector circuit of FIG. 2represents a back side illuminated (BSI) photodetector. A modified frontside illuminated (FSI) photodetector circuit may be realized by CSheteroepitaxy on Si without departing from the scope of the invention.

FIG. 3 is a simplified diagram of a photodetector array circuit device300 according to an embodiment of the present invention. As discussedpreviously, the present invention can include depositing CS materialsoverlying a Si substrate by heteroepitaxy to form a CS material stack.Device 300 can represent a prior fabrication stage of the photodetectorarray circuit (device 201 of FIG. 2 ) that is bonded to the CMOS circuit(device 202 of FIG. 2 ). Here, a CS buffer material 212 is spatiallyconfigured overlying the Si surface 211 of the Si substrate 210.Photodetector device materials, including an n-type CS material 214, anCS absorption material 216, a CS material 218, are spatially configuredoverlying the CS buffer material 212. One or more p-type CS regions 220are configured within one or more portions of the CS material 218. Oneor more isolation trenches 222 are configured within portions of thephotodetector device materials (i.e., layers 214, 216, and 218) andfilled with a dielectric material 226 for optical or electricalisolation, or alternatively or inclusively with other material such as ametal, which can separate individual CS photodetector devices of thearray.

Each of the photodetectors can be configured with metal contacts (orelectrodes) to the n-type CS material 214 and to the p-type CS materials220. In FIG. 3 , a p-contact metal 224 is configured overlying each ofthe p-type CS materials 220, and, although not shown, n-contact metalscan be coupled to the n-type CS material 214. The n-metal contact andcoupling may be made from the topside of the photodetector circuit 212,or from the backside, without departing from the scope of the invention.The p-contact metals 224 can be further coupled to a first terminal 228(e.g., an anode), and the n-contact metals can be coupled to a secondterminal (e.g., a cathode).

According to an example, the present invention provides a circuit for aphotodetector. The photodetector circuit includes a buffer materialformed (or deposited) overlying a surface region of a Si substrate, orthe like. This buffer material can include a CS material deposited onthe surface region of the Si substrate using direct heteroepitaxy suchthat the CS material is characterized by a first bandgap characteristic,a first thermal characteristic, a first polarity, and a firstcrystalline characteristic. Compared to the buffer material, the Sisubstrate is characterized by a second bandgap characteristic, a secondthermal characteristic, a second polarity, and a second crystallinecharacteristic.

In a specific example, the CS material can include InP, InGaAs, galliumarsenide (GaAs), gallium phosphide (GaP), indium gallium arsenidephosphide (InGaAsP), indium aluminum gallium arsenide (InAlGaAs), indiumarsenide (InAs), indium gallium phosphide (InGaP), or a combinationthereof.

The photodetector circuit also includes an array of photodetectors. Thisarray is characterized by N and M pixel elements (i.e., N×M array; N>0,M>0). In a specific example, N is an integer greater than 7, and M is aninteger greater than 0. Each of these pixel elements has acharacteristic length ranging from 0.3 micrometers to 50 micrometers.Also, each of the photodetectors includes an n-type material, anabsorption material overlying the n-type material, and a p-type materialoverlying the absorption material.

In a specific example, the n-type material can include an InP materialwith a silicon impurity having a concentration ranging from 3E17 cm⁻³ to5E18 cm⁻³. The absorption material can include an InGaAs containingmaterial and can be primarily (or substantially) free from any impurity.And, the p-type material can include a zinc impurity or a berylliumimpurity having a concentration ranging from 3E17 cm⁻³ to 5E18 cm⁻³.

In an alternative photodetector CS device structure, the n-type materialincludes a GaAs material comprising a silicon impurity having aconcentration ranging from 3E17 cm⁻³ to 5E18 cm⁻³, the absorptionmaterial includes an InAs quantum dot material, and the p-type materialincludes a zinc impurity or a beryllium impurity or a carbon impurityhaving a concentration ranging from 3E17 cm⁻³ to 1E20 cm⁻³.

Additionally, the photodetector device structure can be configured witha separate absorption material comprising InGaAs or InGaAsP, and amultiplication material comprising InP whereby the multiplicationmaterial generates additional charge carriers by avalanche gain.

The photodetector circuit also includes a first electrode coupled to then-type material and coupled to a first terminal, as well as a secondelectrode coupled to the p-type material and coupled to a secondterminal. This configuration defines each photodetector as a twoterminal device (i.e., having anode and cathode terminals).

The photodetector circuit also includes an illumination regioncharacterized by an aperture region to allow a plurality of photons tointeract with the CS material and be absorbed by a portion of theabsorption material to cause a generation of mobile charge carriers thatproduce an electric current between the first terminal and the secondterminal. In a specific example, the Si substrate is configured to allowthe photons to traverse there through. The illumination region can alsobe configured to be free from any portion of the silicon substrate. Acolor filter can be configured overlying (or otherwise coupled to) theillumination region, and a lens can be configured overlying (orotherwise coupled to) the color filter.

Further, the photodetector circuit is characterized by a responsivitygreater than 0.1 Amperes/Watt and a photodiode quantum efficiencygreater than 10%. The photodetector circuit can be characterized as aBSI device or a FSI depending upon the application.

The photodetector circuit device can further include an analog front-endcircuit, such as a ROIC, coupled to the array of photodetectors. TheROIC includes a first input terminal, a second input terminal, and apixel output. The first and second input terminals are coupled to thefirst and second terminals of the photodetectors, respectively. Thephotodetector circuit can also include analog-to-digital conversionfunctionality (e.g., configured with or as part of the ROIC. There canbe other variations, modifications, and alternatives to the elements andconfigurations discussed above.

Further details of example fabrication methods related to devices 200and 300 are discussed below in reference to FIGS. 4-9 .

FIGS. 4-9 are simplified diagrams illustrating methods of fabricating acompound semiconductor (CS) photodetector circuit device according to anexample of the present invention. In these figures, shared referencenumerals in subsequent figures refer to the same elements as describedin previous figures.

FIG. 4 is a simplified diagram of a device 400 including CS buffermaterials on a Si substrate realized by heteroepitaxy according to anexample of the present invention. In this embodiment, a CS buffermaterial 420 is deposited overlying a surface region 411 of a Sisubstrate 410 in order to nucleate the CS material 420 and to trapand/or filter defects within the buffer material 420 and near theinterface between the CS material 420 and Si surface 411. The initialnucleation and buffer material growth may be carried out with a numberof methodologies, and combinations of methodologies, including, but notlimited to, initial group IV material growth for surface reorderingfollowed by group III-V CS growth for defect trapping; Si surfacepatterning or structuring, that may include formation of various Sicrystal planes, followed by CS nucleation and growth; low-temperature CSnucleation; low-temperature CS nucleation followed by multi-step growthwith temperature grading for defect bending and annihilation; use ofstrained layer superlattices, interfaces with high strain fields, gradedor step-graded materials, or other similar techniques to redirect, trap,convert, and/or annihilate defects.

As shown in device 500 of FIG. 5 , following the formation of the CSbuffer material 420, the photodetector device materials may be depositedoverlying the CS buffer material 420 and Si substrate 410. Thephotodetector device materials can include an n-type CS material 510, aCS absorption material 520, and a CS material 530. In this embodiment,the CS device materials that are deposited overlying the buffer on Si(e.g., device 400 of FIG. 4 ) may form planar photodiode structures forthe photodetector array circuit.

The n-type CS material 510 comprises a Si doping impurity and is formedoverlying the buffer on Si. The CS absorption material 520, which isformed overlying the n-type material 510, is highly absorptive of lightwith a characteristic wavelength or wavelength range of interest. Theabsorption material 520 is primarily free from impurities. The CSmaterial 530, which is formed overlying the absorption material 520, isdeposited without intentional impurity. The various materialsillustrated may comprise of band smoothing layers, diffusion blocklayers, a separate absorption layer, a charge layer, or a multiplicationlayer. Those of ordinary skill in the art will recognize othervariations, modifications, and alternatives.

As shown in device 600 of FIG. 6 , the p-type material 610 for eachphotodetector is formed within a portion of the CS material 530.Depending on the specific CS material used for element 530, the p-typematerial 610 can be formed with diffusion of an impurity material thatmay be zinc, beryllium, or carbon, or the like.

FIG. 7 illustrates the photodetector circuit 700 following thecompletion of the front-end fabrication steps (e.g., as shown previouslyin FIGS. 4-6 ). Isolation trenches 710 may be formed within portions ofthe photodetector device materials (i.e., layers 510-530) for optical orelectrical isolation, and, in combination, to expose the n-type layer510 (e.g., to form one or more n-contact metals). One or more p-contactmetals 720 can be formed overlying the p-type materials 610. Adielectric material 730 may be deposited overlying the p-contact metals720, the p-type materials 610, and the photodetector device materials.In this case, the dielectric material 730 also fills isolation trenches710. Additional vias and trenches may be formed to expose the p-contactmetals 720, and then the vias and trenches may be filled with metalmaterials 740 to provide metal connections to the p-contact metals 720at the exposed surface region of the dielectric material 730. Of course,there can be other variations, modifications, and alternatives.

Photodetector device structures formed could include, but are notlimited to, PIN photodiodes, APDs, UTC-PDs, mesa photodiodes, or planarphotodiodes. Photodetectors could leverage bulk absorptive layers,including, but not limited to, InGaAs, InGaAsP, or could alternativelyleverage quantum wells, quantum dashes, or quantum dots. Those ofordinary skill in the art will recognize other variations,modifications, and alternatives.

FIG. 8 represents an alternative embodiment of a photodetector circuit800 whereby the CS materials are deposited on the Si surface byselective area heteroepitaxy, whereby the Si surface is firstlypatterned with a dielectric material 810 to form recesses, within whichthe CS materials would be selectively deposited on the exposed Sisurface while not depositing on the dielectric material. The materialsmay comprise of similar or identical layers as those described for FIG.7 (denoted by the same reference numerals). As illustrated in FIG. 9 ,the front-end fabrication steps for the photodetector circuit 900following the selective heteroepitaxy of the CS materials (shown in FIG.8 ) may be similar or identical to those steps utilized to form thephotodetector circuit 700 in the embodiment of FIG. 7 (denoted by thesame reference numerals). As shown, the dielectric material 910(combined with dielectric material 810, if not removed) isolates the twoCS material stacks formed by selective area heteroepitaxy.

Selective area heteroepitaxy is beneficial for improving the quality ofthe CS material on Si, for facilitating photodetector fabrication, andalso for realization of novel device structures. Selective areaheteroepitaxy can improve material quality by releasing thermal straincaused by the mismatch in thermal expansion coefficient between the CSmaterials and the Si, and by providing aspect ratio trapping of defectsand dislocations.

The embodiment of FIG. 9 may not require a separate trench isolationstep (shown in FIG. 7 ) due to the isolation provided by the patterneddielectric 810. Some of the dielectric between the CS areas can beremoved by etching or an alternative process, and then these regions canbe filled with materials, such as metals, that would be opaque, toprovide additional optical isolation. Without departing from the scopeof the invention, such trench isolation could alternatively be formed ina backend step following bonding of the photodetector substrate, orchips from the substrate, to a target readout circuit Si CMOS substrate.

FIGS. 10A-10C are simplified diagrams illustrating wafer die patternsaccording to various examples of the present invention. FIG. 10Aillustrates a wafer 1001 with an example die pattern, where eachindividual die (e.g., die 1010) may vary in size/area from small, suchas less than 1 mm×1 mm, to a larger size that is the maximum allowablefor the lithography system used. Within each die, various patterns ofthe dielectric can be leveraged should selective area heteroepitaxy beutilized for CS material growth on Si. Examples can include circularpatterns (shown in die 1002 of FIG. 10B), rectangular patterns (shown indie 1003 of FIG. 10C). Pattern shape and size selection can assist,along with growth optimization and pattern fill factor, to achievehigher material quality. For the rectangular stripe patterns shown indie 1003, circular photodetectors, denoted by the dashed circles (e.g.,photodetector 1020), could be formed following growth by mesa etching orby diffusion, the latter of which would form a planar device. Thepatterns represent the area from which the dielectric, for selectivearea heteroepitaxy, is removed to expose the Si surface below thedielectric.

Other patterns, such as, but not limited to, squares, ovals, trapezoids,different size rectangles, parallelograms, and various polygons could beleveraged without departing from the scope of the invention.

The sequence of steps to complete the realization of such photodetectorsand photodetector arrays, including those represented in the embodimentsof FIG. 2-10C, can be carried out in a number of ways and in differentorder, and the design of the device layers and structure could bevaried, without departing from the scope of the invention.

FIG. 11 is a simplified flow diagram illustrating a method tomanufacture photodetectors and photodetector array circuits according toan example of the present invention. As shown, FIG. 11 illustrates andsummarizes sequences of parallel steps that could be carried out torealize CS on Si photodetectors and photodetector arrays that are thenintegrated with CMOS circuits capable of functions including, but notlimited to, read out, logic, AI, machine learning (ML), signalprocessing, and image processing. In an example, the present methodincludes a front-end photodetector fabrication process 1110 and afront-end CMOS IC fabrication process 1120 performed in parallel.

As shown, the front-end photodetector fabrication process 1110 caninclude providing a substrate 1112 (e.g., Si substrate, SOI substrate,or the like), performing CS on Si heteroepitaxy and forming devicestructures to produce device 1114, and performing metallization toproduce device 1116. The CS on Si heteroepitaxy, device structureformation, and metallization steps can be carried out to realizestructures such as, but not limited to, those described in theembodiments of FIG. 7 or FIG. 9 . Other photodetector variants couldalso be fabricated and then follow a similar sequence of steps forintegration with CMOS circuit wafers. For the front-end IC fabricationprocess 1120, the steps can similarly include providing a substrate 1122(e.g., Si CMOS substrate, or the like), performing IC fabricationprocesses (e.g., ROIC on Si process and/or other IC front-endfabrication) to produce device 1124, and performing metallization toproduce device 1126.

Following front-end fabrication of the photodetector circuits (process1110) and the CMOS circuits (process 1120), the wafers (devices 1116 and1126) could be bonded face-to-face (i.e., a flip-chip bondingconfiguration), as shown by device 1130, leveraging common bondingtechniques such as, but not limited to, oxide-to-oxide andcopper-to-copper (Cu-to-Cu) bonding. The precise steps for back-endfabrication, including bonding integration, could vary depending on thephotodetector structure and photodetector front-end fabricationsequence, and the CMOS device structure and CMOS front-end fabricationsequence, without departing from the scope of the invention.

Following the bonding, back-end fabrications steps may be performed toproduce a processed device 1140 (e.g., device 200 of FIG. 2 ). Suchback-end fabrication steps may include, but are not limited to: removalof the photodetector handle wafer, either partially or entirely bygrinding, etching, or polishing, or a combination therein; applicationof backside contacts, which could be made to either the n-side or p-sideof the photodetector, depending on the orientation of the photodetectorstructure (i.e., whether the photodetector is a PIN or PN structure fromthe top down, or NIP or NP structure from the top down; application ofcolor filters; application of lenses or other optics). The devicestructure could be FSI or BSI and the precise steps and the order of thesteps could vary without departing from the scope of the invention.

Alternatively to the wafer-to-wafer process described, the fabricationof photodetectors bonded to CMOS circuits could also be carried out in achip-to-wafer or chip-to-chip fashion. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

FIG. 12 is a simplified diagram illustrating a plot 1200 of theapproximate absorption spectra for InGaAs material, which is used in thepresent invention, and Si material, which is used in conventional CMOSsensing devices. To prove the method and device, we plotted acompilation of data for the absorption of InGaAs (solid line) and Si(dotted line) over a wide wavelength range to illustrate the benefit andadvantages of the present techniques. As illustrated, the absorption ofInGaAs is higher over the wavelength range considered, and thewavelength range of InGaAs extends to longer wavelength than that forSi. The spectrum illustrated for InGaAs is for an indium composition of0.53 and a gallium composition of 0.47. This composition is commonlyused as it is lattice matched to InP. The absorption wavelength rangefor InGaAs can be extended further to longer wavelength by altering theInGaAs composition, which incorporates strain.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

What is claimed is:
 1. A vehicle apparatus, the device comprising: avehicle comprising a drive mechanism, the drive mechanism beingconfigured to cause the vehicle to move from a first location to asecond location; and a module device comprising a housing, having anexterior region and an interior region, the exterior region having adisplay portion and a sensing portion and a detecting portion; a laserdevice configured to emit electromagnetic radiation having 850 to 1550nm wavelength range and spatially disposed to include an apertureconfigured on the sensing portion; and a circuit for a photodetectorcomprising: a first terminal; a second terminal; a silicon (Si)substrate comprising a surface region; a buffer material comprising acompound semiconductor (CS) material deposited on the surface region ofthe Si substrate using direct heteroepitaxy such that the CS material ischaracterized by a first bandgap characteristic, a first thermalcharacteristic, a first polarity, and a first crystallinecharacteristic, and the silicon substrate is characterized by a secondbandgap characteristic, a second thermal characteristic, a secondpolarity, and a second crystalline characteristic; an array ofphotodetectors, the array being characterized by N and M pixel elements,where N is an integer greater than 7, and M is an integer greater than0; each of the pixel elements having a characteristic length rangingfrom 0.3 micrometers to 30 micrometers, each of the photodetectorscomprising: an n-type material comprising an InP material comprising asilicon impurity having a concentration ranging from 3E17 cm-3 to 5E18cm-3; an absorption material overlying the n-type material, theabsorption material comprising a InGaAs containing material, theabsorption material being primarily free from any impurity; a p-typematerial overlying the absorption material, the p-type materialcomprising a zinc impurity or a beryllium impurity having aconcentration ranging from 3E17 cm-3 to 5E18 cm-3; a first electrodecoupled to the n-type material and coupled to the first terminal; asecond electrode coupled to the p-type material and coupled to thesecond terminal to define a two terminal device; an illumination regioncharacterized by an aperture region to allow a plurality of photons tointeract with the CS material and be absorbed by a portion of theabsorption material to cause a generation of mobile charge carriers thatproduce an electric current between the first terminal and the secondterminal; a responsivity (Amperes/Watt) greater than 0.1 Amperes/Wattcharacterizing the circuit; and a photodiode quantum efficiency greaterthan 10% characterizing the circuit.
 2. The apparatus of claim 1 whereinthe wavelength range is 940 nm.
 3. The apparatus of claim 1 wherein themodule device is configured on an exterior region of the vehicle, theexterior region being a roof portion of the vehicle.
 4. The apparatus ofclaim 1 wherein the vehicle is selected from a boat, a drone, anairplane, a truck, an automobile, an autonomous vehicle, or a hybridvehicle.
 5. The apparatus of claim 1 wherein the module device comprisesa classifier module coupled within an interior region of the housing,the classifier module including a classification of one or more classesincluding a speed sensing, image sensing, facial recognition, distancesensing, acoustics sensing, thermal sensing, color sensing, a biologicalsensor, a gravitational sensing, or a mechanical motion sensing.
 6. Theapparatus of claim 1 wherein the Si substrate is configured to allow thephotons to traverse there through.
 7. The apparatus of claim 1 whereinthe illumination region is free from any portion of the siliconsubstrate.
 8. The apparatus of claim 1 wherein the laser devicecomprises a VCSEL array device or a laser device coupled to a mirrordevice.
 9. The apparatus of claim 1 wherein the circuit comprises acolor filter overlying the illumination region and a lens overlying thecolor filter.
 10. The apparatus of claim 1 wherein the CS materialcomprises InP, InGaAs, GaAs, GaP, InGaAsP, InAlGaAs, InGaP, or acombination thereof.
 11. The apparatus of claim 1 wherein eachphotodetector is configured with a separate absorption materialcomprising InGaAs or InGaAsP, and a multiplication material comprisingInP whereby the multiplication material generates additional chargecarriers by avalanche gain.
 12. The apparatus of claim 1 wherein theabsorption material comprises InAs quantum dot or quantum dashcontaining material.
 13. The apparatus of claim 1 wherein each of thephotodetectors comprises: an n-type material comprising a GaAs materialcomprising a silicon impurity having a concentration ranging from 3E17cm-3 to 5E18 cm-3; an absorption material overlying the n-type material,the absorption material comprising InAs quantum dot material; a p-typematerial overlying the absorption material, the p-type materialcomprising a zinc impurity or a beryllium impurity or a carbon impurityhaving a concentration ranging from 3E17 cm-3 to 1E20 cm-3.
 14. Theapparatus of claim 1 wherein the circuit is characterized as a back sideilluminated (BSI) device.
 15. The apparatus of claim 1 wherein thecircuit is characterized as a front side illuminated (FSI) device. 16.The apparatus of claim 1 wherein the module device comprises: a readoutintegrated circuit comprising: a first input terminal coupled to thefirst terminal; a second input terminal coupled to the second terminal;and a pixel output.
 17. The apparatus of claim 16 wherein module devicecomprises an analog front end circuit coupled to the first inputterminal and the second input terminal.
 18. The apparatus of claim 17wherein the module device comprises analog to digital conversion.
 19. Avehicle apparatus, the apparatus comprising: a vehicle comprising adrive mechanism, the drive mechanism being configured to cause thevehicle to move from a first location to a second location; and a moduledevice configured to an exterior region of the vehicle, the moduledevice comprising a housing, having an exterior region and an interiorregion, the exterior region having a display portion and a sensingportion and a detecting portion; a laser device spatially disposed toinclude an aperture configured on the sensing portion; and aphotodetector array circuit having a first terminal, a second terminal,and a plurality of photodetectors, each of the photodetectors comprisingan n-type material compound semiconductor (CS) material, a CS absorptionmaterial overlying the n-type material, a p-type CS material overlyingthe absorption material, a first electrode coupled to the n-typematerial and coupled to the first terminal; and a second electrodecoupled to the p-type material and coupled to the second terminal;wherein the photodetector array circuit includes an illumination regionconfigured underlying the n-type CS materials of the plurality ofphotodetectors.
 20. A vehicle apparatus, the apparatus comprising: avehicle comprising a drive mechanism, the drive mechanism beingconfigured to cause the vehicle to move from a first location to asecond location; and a module device configured to an exterior region ofthe vehicle, the module device comprising a housing, having an exteriorregion and an interior region, the exterior region having a displayportion and a sensing portion and a detecting portion; a laser devicespatially disposed to include a first aperture configured on the sensingportion; an image sensor device spatially disposed to include a secondaperture configured on the detecting portion, the image sensor devicecomprising a photodetector device; wherein the photodetector deviceincludes a first terminal, a second terminal, and a plurality ofphotodetectors, each of the photodetectors comprising an n-type materialcompound semiconductor (CS) material, a CS absorption material overlyingthe n-type material, a p-type CS material overlying the absorptionmaterial, a first electrode coupled to the n-type material and coupledto the first terminal; and a second electrode coupled to the p-typematerial and coupled to the second terminal; wherein the photodetectordevice includes an illumination region configured underlying the n-typeCS materials of the plurality of photodetectors; and a readoutintegrated circuit (ROIC) coupled to the photodetector device, the ROIChaving a first input terminal, a second input terminal, and a pixeloutput; wherein the first input terminal is coupled to the firstterminal and the second input terminal is coupled to the second terminalat an interface region between the photodetector device and the ROIC.